Monday 28 December 2015

In response to Issue 53, Article 5, entitled Red-eared sliders invade Auckland city waterways dated Sunday Dec 13, 2015, in the I received the following letter in response which was published the next day in the New Zealand Herald. - via Herp Digest

The letter:

The headline “Turtles invade Auckland city waterways” was way off the mark.  There are a lot of reasons for this.  Here are a few:

Prior to importation being banned in 1965 about 30,000 red-ear slider turtles had been brought into the country.  Since then about 2000 turtles have been bred per year in New Zealand.  That’s a total of about 130,000 animals.  If they were able to survive and reproduce in the wild there would now be many millions of them running around Auckland yet only a handful are found each year.

There are two reasons why we are NOT being invaded.  The first is that turtles cannot reproduce here without human help.  Turtle eggs require high temperatures and lots of moisture to hatch.  The few areas where it’s warm enough are inevitably too dry for the eggs to survive.  There have been a few cases of turtle eggs hatching outdoors but they have always been situations near a north facing rock wall or other heat sink that was watered consistently.  The sex of hatchling turtles is controlled by ground temperatures so even those situations are only able to produce males because of the cooler temperatures.

The other problem for turtles in New Zealand is that it is too cool in the summer and too warm in the winter.  The cool temperatures in summer prevent them from being able to warm up enough to digest the vegetation they eat (they do NOT eat live fish, birds or eggs) and the relatively warm winter temperatures keep them from hibernating properly so they lose weight and die of starvation and disease after about four years.

Turtles are also no threat to the few natural wetlands in New Zealand because the water is too cool for them to be able to warm up enough to eat.  Turtles might survive for a few years in warmer man made ponds, backwaters of the Waikato River and the numerous weed choked canals in the Hauraki Plains but, even there, they inevitably die after a few years.

Hopefully when the Auckland Council goes through their “major pest management review” they will consult with someone that is actually familiar with the biology of turtles.

Dr. Mark Feldman
Dr. Feldman has regularly spoken at the TSA conference concerning updates to recommendations on drugs and doses to induce egg laying in turtles.  His research is carried out at the largest turtle farm in the USA where they have large numbers of turtles available to develop new drugs and determine dosages, and in New Zealand where he has maintained a colony of turtles for 25 years so he can detect any long term side effects. He has also spoken in Australasia at the vertebrate pest conference on real and perceived threats of introduced turtle species, published articles on the real and perceived threats of turtles under New Zealand conditions and consulted for, and spoken at, a conference of the US Fish and Wildlife service on American turtle farms and their relevance to turtle conservation.

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